The present invention relates to an air-bag arrangement, and more particularly relates to an air-bag arrangement adapted to be controllably vented.
It is known that it is desirable to vent an air-bag provided for use in a motor vehicle to protect an occupant of the vehicle in the event that an accident should occur, especially if the air-bag is of the type intended to provide protection in the event that a front impact should occur.
An air-bag that is intended to provide protection in the case that a front impact should occur is generally located so that, when inflated, the air-bag is positioned in front of the occupant to be protected. During the front impact the vehicle decelerates suddenly. Due to inertia, the occupant of the vehicle tends to continue moving, and thus the occupant of the vehicle is, in effect, moving forwardly relative to the rest of the vehicle. The function of the air-bag is to decelerate the occupant, preferably in such a way that the occupant suffers no injury. The air-bag must be inflated very swiftly and thus, typically contains relatively high-pressure gas. If the air-bag were not vented, then because of the high gas pressure within it, the air-bag would not decelerate the occupant in a desired manner. Thus many air-bags are provided with vent holes formed in them so that, when the air-bag is struck by the occupant, gas can escape from the air-bag through the vent hole or holes, so that the air-bag serves the function of decelerating the occupant more gently, to avoid such injury.
In many cases it is desirable to be able to control the degree of venting, or the time at which venting commences. For example, if an occupant of a seat is out of the ordinary seating position and is, for example leaning forwardly, then it is desirable to commence venting of the air-bag at a very early stage during its inflation. Varying degrees of venting may be desirable depending upon the weight and/or size of the occupant to be protected by the air-bag.
Various mechanisms have been proposed previously for the controllable venting of an air-bag.
The present invention seeks to provide an improved air-bag arrangement.